Terminal Device, Base Station Device, Communication System, and Communication Method Adapted to Transmit Location Information

1. A terminal device comprising: a retrieval unit that retrieves location information and time information; a communication unit that transmits the location information retrieved by the retrieval unit to a base station device and receives from the base station device a threshold value for a distance of travel determined by a traffic of communication; a storage that stores the location information transmitted from the communication unit and stores the retrieved time information; a derivation unit that derives the distance of travel based on the location information stored in the storage and the location information newly retrieved by the retrieval unit; and a controller that causes the communication unit to transmit the location information newly retrieved by the retrieval unit, if the distance of travel derived by the derivation unit exceeds the threshold value; if the distance of travel derived by the derivation unit is equal to or less than the threshold value, the controller stops transmission of the location information newly retrieved by the retrieval unit, and if a predetermined period of time has elapsed since the time indicated by the time information stored in the storage, the controller transmits the location information newly retrieved by the retrieval unit.

2. The terminal device according to claim 1 , wherein the derivation unit derives the distance of travel by calculating a linear distance between the location information stored in the storage and the location information newly retrieved by the retrieval unit.

3. The terminal device according to claim 2 , wherein the retrieval unit retrieves time information along with the location information, the storage stores the retrieved time information along with the location information transmitted from the communication unit, if the distance of travel derived by the derivation unit is equal to or less than the threshold value, the controller stops transmission of the location information newly retrieved by the retrieval unit, and if a predetermined period of time has elapsed since the time indicated by the time information stored in the storage, the controller transmits the location information newly retrieved by the retrieval unit.

4. A base station device comprising: a communication unit that performs communication with a terminal device; a measurement unit that measures a traffic of communication in the communication unit; and a controller that determines a threshold value for a distance of travel of the terminal device in accordance with the traffic measured by the measurement unit and causes the communication unit to transmit the determined threshold value to the terminal device, wherein the communication unit receives location information that is transmitted if the terminal device travels beyond the threshold value, the communication unit stops receiving location information that is transmitted if the terminal device travels equal to or below the threshold value, the communication unit receives location information that is transmitted if a predetermined period of time has elapsed, and the controller controls the threshold value such that the heavier the traffic, the larger the threshold value.

5. A communication system comprising: a base station device; and a terminal device that transmits retrieved location information to the base station device and receives from the base station device a threshold value for a distance of travel, wherein the base station device includes: a measurement unit that measures a traffic of communication with the terminal device; and a controller that determines a threshold value such that the heavier the traffic measured by the measurement unit, the larger the threshold value, and transmits the determined threshold value to the terminal device, and wherein the terminal device includes: a retrieval unit that retrieves location information and time information; a communication unit that transmits the location information retrieved by the retrieval unit to a base station device and receives from the base station device a threshold value for a distance of travel determined by a traffic of communication; a storage that stores the transmitted location information and stores the retrieved time information; a derivation unit that derives the distance of travel based on the location information stored in the storage and the newly retrieved location information; and a controller that causes the newly retrieved location information to be transmitted, if the distance of travel derived by the derivation unit exceeds the threshold value; if the distance of travel derived by the derivation unit is equal to or less than the threshold value, the controller stops transmission of the location information newly retrieved by the retrieval unit, and if a predetermined period of time has elapsed since the time indicated by the time information stored in the storage, the controller transmits the location information newly retrieved by the retrieval unit.